LED device for wide beam generation

ABSTRACT

An apparatus and method is characterized by providing an optical transfer function between a predetermined illuminated surface pattern, such as a street light pattern, and a predetermined energy distribution pattern of a light source, such as that from an LED. A lens is formed having a shape defined by the optical transfer function. The optical transfer function is derived by generating an energy distribution pattern using the predetermined energy distribution pattern of the light source. Then the projection of the energy distribution pattern onto the illuminated surface is generated. The projection is then compared to the predetermined illuminated surface pattern to determine if it acceptably matches. The process continues reiteratively until an acceptable match is achieved. Alternatively, the lens shape is numerically or analytically determined by a functional relationship between the shape and the predetermined illuminated surface pattern and predetermined energy distribution pattern of a light source as inputs.

RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §120 to U.S.patent application Ser. No. 13/540,477 filed on Jul. 2, 2012, which wasa continuation of U.S. patent application Ser. No. 13/109,609 filed onMay 17, 2011, which was a continuation of U.S. patent application Ser.No. 12/690,794 filed on Jan. 20, 2010 now U.S. Pat. No. 7,942,559; whichwas a division of U.S. patent application Ser. No. 11/711,218 filed onFeb. 26, 2007 now U.S. Pat. No. 7,674,018, which claims priority under35 U.S.C. §119 to U.S. Provisional Patent Application Ser. No.60/777,310, filed on Feb. 27, 2006; U.S. Provisional Patent ApplicationSer. No. 60/838,035, filed on Aug. 15, 2006; and U.S. Provisional PatentApplication Ser. No. 60/861,789, filed on Nov. 29, 2006, each of whichare incorporated herein by reference. This application is also relatedto U.S. patent application Ser. No. 12/690,821 filed on Jan. 20, 2010now U.S. Pat. No. 7,993,036; and U.S. patent application Ser. No.13/109,582 filed on May 17, 2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of apparatus and methods for usinglight emitting diodes (LEDs) or other light sources to generatepredetermined wide profile two dimensional illumination patterns using alight source which has been optically modified to provide acorresponding wide profile beam or a flat array of multiple ones of suchmodified light sources.

2. Description of the Prior Art

The initial investment cost of LED illumination is expensive whencompared with traditional lighting means using cost per lumen as themetric. While this may change over time, this high cost places a premiumon collection and distribution efficiency of the LED optical system. Themore efficient the system, the better the cost-benefit comparison withtraditional illumination means, such as incandescent, fluorescent andneon.

A traditional solution for generating broad beams with LEDs is to useone or more reflectors and/or lenses to collect and then spread the LEDenergy to a desired beam shape and to provide an angled array of suchLEDs mounted on a curved fixture. Street light illumination patternsconventionally are defined into five categories, Types I-V. Type 1 is anoblong pattern on the street with the light over the center of theoblong. Type II is a symmetric four lobed pattern with the light overthe center of the lobed pattern. Type III is a flattened oblong patternwith the light near the flattened side of the oblong. Type IV isparabolic pattern with a flattened base with the light near theflattened base. Type V is a circular pattern with the light over thecenter of the circle. Any asymmetric aspect of these categoricalpatterns is obtained by mounting the light sources in a curved armatureor fixture. By curving or angling the fixture to point the LEDs or lightsources in the directions needed to create a broad or spread beam onto asurface, such as a street, a portion of the light is necessarilydirected upward away from the street into the sky. Hence, all airplanepassengers are familiar with the view of a lighted city at night onapproach. This often dazzling display is largely due to street lightsand more particularly to street lights that have canted fixtures tocreate spread beams and hence collectively direct a substantial amountof light skyward toward approaching aircraft. In an efficiently lightedcity, the city would appear much darker to aircraft, because the streetlights should be shining only onto the street and not into the sky. Thedazzling city lights seen from aircraft and hill tops may be romantic,but represent huge energy losses, unnecessary fuel usage, and tons ofunnecessary green house gas emissions from the electrical plants neededto generate the electricity for the wasted light.

Another technique is to use a collimating lens and/or reflector and asheet optic such as manufactured by Physical Devices Corporation tospread the energy into a desired beam. A reflector has a predeterminedsurface loss based on the metalizing technique utilized. Lenses whichare not coated with anti-reflective coatings also have surface lossesassociated with them. The sheet material from Physical Optics has aboutan 8% loss.

One example of prior art that comes close to a high efficiency system isthe ‘Side-emitter’ device sold by Lumileds as part of their LEDpackaging offerings. However, the ‘side-emitter’ is intended to create abeam with an almost 90 degree radial pattern, not a forward beam. It hasinternal losses of an estimated 15% as well. Another Lumileds LED,commonly called a low dome or bat wing LED, has a lens over the LEDpackage to redirect the light, but it is to be noted that it has noundercut surface in the lens for redirecting the light from the LEDwhich is in the peripheral forward solid angle. Similarly, it is to benoted that the conventional 5 mm dome lens or packaging provided forLEDs lacks any undercut surface in the dome at all.

What is needed is an device that creates a wide angle beam, even thepossibility of a nonradially symmetric beam, that can be created with adesign method that allows the al designer to achieve a smooth beamprofile which is not subject to the inherent disadvantages of the priorart.

BRIEF SUMMARY OF THE INVENTION

The illustrated embodiment of the invention includes a method ofproviding a predetermined illuminated surface pattern from apredetermined energy distribution pattern of a light source comprisingthe steps of defining an estimated optical transfer function of a lensshape; generating an energy distribution pattern using the estimatedoptical transfer function of a lens shape from the predetermined energydistribution pattern of the light source; generating a projection of theenergy distribution pattern onto the illuminated surface; comparing theprojection of the energy distribution pattern to the predeterminedilluminated surface pattern; modifying the estimated optical transferfunction of the lens shape; repeating the steps of generating the energydistribution pattern using the estimated optical transfer function ofthe lens shape from the predetermined energy distribution pattern of thelight source, generating the projection of the energy distributionpattern onto the illuminated surface, and comparing the projection ofthe energy distribution pattern to the predetermined illuminated surfacepattern until acceptable consistency between the projection of theenergy distribution pattern and the predetermined illuminated surfacepattern is obtained; and manufacturing a lens with the last obtainedestimated optical transfer function.

In one embodiment the predetermined illuminated surface pattern is astreet lighting pattern and the predetermined energy distributionpattern of the light source is a LED Lambertian pattern so that what ismanufactured is a lens for a street light.

The method further comprises the step of assembling a plurality of lightsources optically each combined with the manufactured lens to form acorresponding plurality of devices, each having an identical energydistribution pattern, to provide a linearly additive array of devices toproduce the predetermined illuminated surface pattern.

In one embodiment each array is manufactured as a modular unit and themethod further comprises the step of scaling the intensity of theillumination pattern on the target surface without substantialmodification of the illumination pattern by modular scaling of thearrays into larger or smaller collections.

The illustrated embodiment of the invention is also an improvement in anapparatus for providing an optical transfer function between apredetermined illuminated surface pattern and a predetermined energydistribution pattern of a light source comprising a lens having a shapedefined by the optical transfer function which is derived by generatingan energy distribution pattern using the predetermined energydistribution pattern of the light source and then generating aprojection of the energy distribution pattern onto the illuminatedsurface from the energy distribution pattern, which projectionacceptably matches the predetermined illuminated surface pattern.

In one embodiment the predetermined illuminated surface pattern is astreet lighting pattern and the predetermined energy distributionpattern of the light source is a LED Lambertian pattern.

An embodiment of the claimed invention also includes a light sourcecombined with the lens.

The illustrated embodiment is also an improvement in a lens for use inan apparatus for providing a predetermined illuminated surface patternfrom a predetermined energy distribution pattern of a light sourcecomprising an undercut surface defined on the lens, the lens having abase adjacent to the light source, a lens axis and a surface between thebase and lens axis, the undercut surface extending from the base of thelens at least partially along the surface of the lens toward the lensaxis to generate an energy distribution pattern using the predeterminedenergy distribution pattern of the light source which will then generatea projection of the energy distribution pattern onto the illuminatedsurface, which projection acceptably matches the predeterminedilluminated surface pattern.

The undercut surface comprises portions which refract light and whichtotally internally reflect light from the light source into the energydistribution pattern.

The undercut surface comprises portions which direct light from thelight source into a broad spread beam.

The illustrated embodiment is also an improvement in an apparatus forproviding an optical transfer function between a predeterminedilluminated surface pattern and a predetermined energy distributionpattern of a light source comprising an undercut surface of a lenshaving a shape defined by the optical transfer function which shape isderived by generating an energy distribution pattern using thepredetermined energy distribution pattern of the light source and thengenerating a projection of the energy distribution pattern onto theilluminated surface from the energy distribution pattern, whichprojection acceptably matches the predetermined illuminated surfacepattern.

The illustrated embodiment is also an improvement in a lens surface foruse in an apparatus for providing a predetermined illuminated surfacepattern from a predetermined energy distribution pattern of a lightsource, where the lens is characterized by an energy distributionpattern with two opposing sides, the improvement comprising a complexprism defined as part of the lens surface, the complex prism beingarranged and configured to transfer energy from one side of the energydistribution pattern to the opposing side to render the energydistribution pattern asymmetric with respect to the two opposing sides.

The illustrated embodiment is also an array for providing apredetermined illuminated surface pattern comprising a plurality oflight emitting devices for providing the predetermined illuminatedsurface pattern, each device having an identical energy distributionpattern which produces the predetermined illuminated surface pattern, acircuit driver coupled to each of the devices, and a planar carrier inwhich the plurality of light emitting devices are arranged to provide aspatially organization of the array to collectively produce a linearlyadditive illumination pattern matching the predetermined illuminatedsurface pattern.

Each array is a modular unit capable of being readily combined with alike array and further comprising a collection of arrays for scaling theintensity of the illumination pattern on the target surface withoutsubstantial modification of the illumination pattern by modular scalingof the arrays into a larger or smaller collection.

The array further comprises a plurality of circuit drivers, one for eachdevice and where the plurality of circuit drivers are mounted on orattached to the carrier. The carrier comprises a printed circuit boardto which the plurality of circuit drivers and devices are coupled, acover for sealing the printed circuit board, circuit drivers and devicesbetween the cover and carrier. The devices are optionally provided witha flange or an indexing flange and where the devices are angularlyoriented with respect to the cover and carrier by the indexing flange.The printed circuit board, circuit drivers and devices are optionallysealed between the cover and carrier by means of a potting compounddisposed between the cover and carrier in which potting compound thecircuit drivers and devices as coupled to the printed circuit board areenveloped to render the array submersible.

Another embodiment of the invention is a luminaire for a street light toprovide a predetermined illumination pattern on a street surfacecomprising a lighting fixture, and a plurality of arrays of lightemitting devices disposed in the lighting fixture, each array forproviding the predetermined illumination pattern on the street surface.

The array in the luminaire for providing a predetermined illuminatedsurface pattern comprises a plurality of light emitting devices forproviding the predetermined illuminated surface pattern, each devicehaving an identical energy distribution pattern which produces thepredetermined illuminated surface pattern, a circuit driver coupled toeach of the devices; and a planar carrier in which the plurality oflight emitting devices are arranged to provide a spatially organizationof the array to collectively produce a linearly additive illuminationpattern matching the predetermined illuminated surface pattern.

In one embodiment each of the light emitting devices in the luminairecomprises a light source and a lens with a lens surface, the lens forproviding the predetermined illuminated surface pattern from apredetermined energy distribution pattern of a light source, where thelens is characterized by an energy distribution pattern with twoopposing sides, the lens surface comprising a complex prism defined aspart of the lens surface, the complex prism being arranged andconfigured to transfer energy from one side of the energy distributionpattern to the opposing side to render the energy distribution patternasymmetric with respect to the two opposing sides.

In another embodiment each of the light emitting devices in theluminaire comprises a light source and a lens with a lens surface, thelens for providing the predetermined illuminated surface pattern from apredetermined energy distribution pattern of a light source, the lensfor providing an optical transfer function between the predeterminedilluminated surface pattern and the predetermined energy distributionpattern of a light source, the lens having an undercut surface with ashape defined by the optical transfer function which shape is derived bygenerating an energy distribution pattern using the predetermined energydistribution pattern of the light source and then generating aprojection of the energy distribution pattern onto the illuminatedsurface from the energy distribution pattern, which projectionacceptably matches the predetermined illuminated surface pattern.

In one embodiment each of the light emitting devices in the luminairecomprises a light source and a lens with a lens surface, the lens forproviding the predetermined illuminated surface pattern from apredetermined energy distribution pattern of a light source, the lenshaving an undercut surface, the lens having a base adjacent to the lightsource, a lens axis and a surface between the base and lens axis, theundercut surface extending from the base of the lens at least partiallyalong the surface of the lens toward the lens axis to generate an energydistribution pattern using the predetermined energy distribution patternof the light source which will then generate a projection of the energydistribution pattern onto the illuminated surface, which projectionacceptably matches the predetermined illuminated surface pattern.

In another embodiment each of the light emitting devices in theluminaire comprises a light source and a lens with a lens surface, thelens for providing the predetermined illuminated surface pattern from apredetermined energy distribution pattern of a light source, the lenshaving a shape defined by the optical transfer function which is derivedby generating an energy distribution pattern using the predeterminedenergy distribution pattern of the light source and then generating aprojection of the energy distribution pattern onto the illuminatedsurface from the energy distribution pattern, which projectionacceptably matches the predetermined illuminated surface pattern.

Another one of the illustrated embodiments is a luminaire for a streetlight to provide a predetermined illumination pattern on a streetsurface, the predetermined illumination pattern having a definedhorizon, comprising a lighting fixture, and a plurality of planar arraysof light emitting devices disposed in the lighting fixture, each arrayfor providing the predetermined illumination pattern on the streetsurface with substantial reduction of light directed from the luminaireto the horizon or above.

The illustrated embodiment of the invention is comprised of a lightsource, such as a light emitting diode (LED) and a lens. It is to beunderstood that for the purposes of this specification that a “lens” isto be understood throughout as an optical element which is capable ofrefraction, reflection by total internal reflecting surfaces or both.Hence, the more general term, “optic” could be used in thisspecification interchangeably with the term, “lens”. The lens ischaracterized by directing light from the light source into a smooth,broad beam, which when projected onto an illumined surface has a 50percent of maximum foot-candle measurement at an angle greater than 15degrees from the centerline of the illumination pattern, i.e. a 30degree full width, half maximum. The lens comprises a transparent ortranslucent “blob-like” or dimpled-puddle shape, such as plastic orglass, that encompasses the light source or LED emitter to generate ahigh angle intensity wide beam without, in the preferred embodiment,adding any additional surface losses, either reflective or refractivethan the LED would cause itself in this configuration of the invention.Almost all the energy of the LED is directed into the beam withoutlosses much in excess of those generated by the LED without the lensdeployed.

The lens comprises a transparent or translucent “blob-like” ordimpled-puddle shape, which produces a high angle intensity wide beamwithout adding any additional surface losses, either reflective orrefractive than the LED would cause itself in this configuration of theinvention. Almost all the energy of the LED is directed into the beamwithout losses much in excess of those generated by the LED without thelens deployed.

In one embodiment the lens is separate from the LED and is glued,affixed or disposed on the light source or original LED protective domewith an index matching material so as to virtually eliminate the seam orany optical discontinuity between the two. In another embodiment thelens is manufactured as the protective dome of the LED.

The lens is characterized by a “blob” zone which is a smallconcentrating zone that is formed along the desired primary director ofthe lens and light source. The blob zone comprises a surface portion ofthe lens which collects the light rays emitted by the LED and sends themalong a predetermined direction dependent on the desired beam angle. Thenearby surrounding surface portion of the lens also collects light fromthe LED emitter and bends it toward the preferential direction.

The blob zone comprises has a central forward cross-section whichsmoothly apportions light from a directed zone to the centerline. Theportion of the lens which collects the peripheral light of the LEDemitter either bends the light rays toward the preferential directionand/or internally reflects the light rays through the forward surface ofthe lens.

In one embodiment the lens produces a beam that is a function of theazimuthal angle of the beam and thus the lens has a cross-section whichvaries as function of the azimuthal angle around the optical axis. Inthe illustrated embodiment the azimuthal light pattern has a multiplelobed distribution of intensity.

In one embodiment of this type the lens also directs the beam in one ormore directions offset from the projected centerline of the device. Thelens includes additional surface shapes or a complexly shaped prism thatadd further control to the beam composition. Such additional surfaceshapes include facets, a multiple surface Fresnel type flattening ofshape or prism, diffusing techniques or other lens surface enhancements,modifications or treatments.

One major advantage of a device of the invention is the ability togenerate the required beam pattern with an array of LEDs which aremounted on a flat or planar plate, which most likely would be parallelto the street or floor. Thus eliminating the need for a complexarmature. The illustrated embodiment further comprises a plurality oflight sources or LEDs and corresponding lenses as describe abovecombined into a flat array of bars or plates to provide thermal andelectrical distribution required for the LEDs as well as provide meansfor sealing the array from environmental damage. The apparatus furthercomprises circuitry to drive the LEDs included in the array. It iscontemplated that each of the lenses are individually rotated to createa beam pattern for the flat array that is unique from the devicesthemselves, including all degrees of freedom, e.g. separately determinedtranslation, tilt and yaw for each lens. The array could comprisesimilarly colored LEDs, white or otherwise, or optionally variouscolored LEDs.

The bars or plates each comprise an extruded or die-cast bar of aluminumor other thermally conductive material to which the LEDs are bondeddirectly, and a printed circuit board to connect the LEDs to a powersource. In one embodiment the circuit board is laminated to the extrudedor die-cast bar.

Each LED optionally incorporates a skirt, which is utilized to provide asealed array with a cover, potting compound or other covering means.

The invention further comprises a method of providing a light patternusing any one of the devices or arrays described above.

While the apparatus and method has or will be described for the sake ofgrammatical fluidity with functional explanations, it is to be expresslyunderstood that the claims, unless expressly formulated under 35 USC112, are not to be construed as necessarily limited in any way by theconstruction of “means” or “steps” limitations, but are to be accordedthe full scope of the meaning and equivalents of the definition providedby the claims under the judicial doctrine of equivalents, and in thecase where the claims are expressly formulated under 35 USC 112 are tobe accorded full statutory equivalents under 35 USC 112. The inventioncan be better visualized by turning now to the following drawingswherein like elements are referenced by like numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of one embodiment of the invention in which asection line B-B is defined. This embodiment is radially symmetric.

FIG. 2 is the side cross sectional view depicted in FIG. 1 throughsection lines ‘B-B’.

FIG. 3 is a polar candela plot of the embodiment of the inventiondescribed in FIGS. 1 and 2. The zero direction is the centerline of thedevice.

FIG. 4 is a side view of the embodiment of the invention described inFIGS. 1-3 showing a sample of rays traced from the source of the LEDemitter through the al portion of the device.

FIG. 5 is a top view of another embodiment where the device is notradially symmetric. This view illustrates an embodiment which has twohorizontally opposed lobes of the ‘blob’ lens.

FIG. 6 is an isometric view of the device of FIG. 5 more clearlydescribing its nonradially symmetric shape.

FIG. 7 is a side plan view of the device of FIG. 5 as seen parallel tosection line D-D showing the reversal or undercut in the outline of thelens.

FIG. 8 is a side plan view that is rotated 90 degrees from the side viewof FIG. 7.

FIG. 9 is a cross-sectional view through section line ‘D-D’ of thedevice described in FIG. 5. This cross-section shows the LED in additionto the lens.

FIG. 10 is the two dimensional iso-footcandle plot of the device ofFIGS. 5-9. This diagram illustrates the nonradially symmetric output ofthe device.

FIG. 11 is the iso-candela plot of the device of FIGS. 5-9 showingmultiple plots of the device in different planes.

FIG. 12 is a side view of a ray tracing of the device of FIGS. 5-9showing the rays traced from the LED emitter through the lens.

FIG. 13 is a side view of the same ray tracing shown in FIG. 12, from aview azimuthally rotated 90 degrees from the view of FIG. 12.

FIG. 14 is an exploded perspective view of a light module comprised ofmultiple devices of a preferred embodiment of the invention.

FIG. 15 is a perspective view of the assembled device of FIG. 14, a flatmodular light bar.

FIG. 16 is a perspective view of another preferred embodiment of theinvention in which the device is asymmetric and creates a light patternthat is offset from a centerline of the LED.

FIG. 17 is a top plan view of the device of FIG. 16.

FIG. 18 is a cross sectional side view of the device of FIGS. 16 and 17as seen through section lines E-E of FIG. 17.

FIG. 19 is a side plan view of the device of FIGS. 17-18.

FIG. 20 is a side plan view of the device of FIGS. 17-19 as seen from aplane orthogonal to that seen in FIG. 19.

FIG. 21 is a perspective view of another embodiment of the inventionusing a complexly shaped prism. This embodiment is for streetlight andsimilar applications. It is azimuthally asymmetric and is oriented inthe figure to show the ‘curb’ side of the streetlight or that side towhich less light is directed.

FIG. 22 is a rotated perspective view of the device depicted in FIG. 21showing the ‘street’ side of the device or that side of the device towhich more light is directed.

FIG. 23 is a ‘bottom’ view of the device of FIGS. 21 and 22 showing the‘street’ side on the right of the view and the curb side on the left ofthe view.

FIG. 24 is a side plan view of the embodiment of the invention describedin FIGS. 21-23 showing in phantom outline the LED on which the lens ofthe device is mounted.

FIG. 25 is a rotated side plan view of the device of FIGS. 21-24orthogonal to the view of FIG. 24.

FIG. 26 is a rotated side plan view of the device of FIGS. 21-25orthogonal to the view of FIG. 25.

FIG. 27 is a side view of a three dimensional iso-candela mapped plot ofthe output of a device of FIGS. 21-26, clearly showing the azimuthallyasymmetric output of the device. The ‘street’ side of the beam isdepicted to the right in the drawing and the curb side to the left. Theplot illustrates that the invention can create a beam profile thatgenerates the full-cutoff beam type required by IES standards forroadway and outdoor lighting.

FIG. 28 is a rotated perspective view of the iso-candela map of FIG. 27showing the output of the device as seen from the ‘curb’ side and fromabove the device. It shows the bias of the beam toward the street anddown the curb line.

FIG. 29 is a two dimensional iso-foot-candle plot of the light beamprojected onto the ‘street’ from a device of the invention. This showsthe non-radially symmetric output of a device of FIGS. 21-26. Thedesigner has the freedom to control the shape of the lens to alter theoutput to match the requirements of the lighting task.

FIG. 30 is a cross-sectional view of a device of FIGS. 21-26 overlaid ona sample ray trace of the energy radiating from the LED emitter. Theview of FIG. 30 is the mirror image of the view of FIG. 25. This view isupside down with the ‘street’ side facing to the left and above andshows refraction and reflection of various surfaces of the lens.

FIG. 31 is a cross-sectional view of a device of FIGS. 21-26 overlaid ona sample ray trace of the energy radiating from the LED emitter. This isa view similar to the view of FIG. 24. FIG. 31 is a cross-sectional viewof the curb side of the device.

FIG. 32 is the cross-sectional view of the device of FIGS. 21-26 as seenthrough section lines F-F of FIG. 23. This view illustrates the assemblyof the device of FIGS. 21-26 with the LED.

FIG. 33 is a block diagram showing the steps of a method where atransfer function is employed.

The invention and its various embodiments can now be better understoodby turning to the following detailed description of the preferredembodiments which are presented as illustrated examples of the inventiondefined in the claims. It is expressly understood that the invention asdefined by the claims may be broader than the illustrated embodimentsdescribed below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before turning to the specifically illustrated examples shown in thedrawings, we consider the various embodiments of the invention in moregeneral terms. The illustrated embodiment of the invention uses lightemitting diodes (LED), or other light sources, in a device that directsthe energy from the LED into a smooth, broad beam. A broad beam can bestbe described as a beam which provides an illumination pattern on thesurface intended to be illuminated, (e.g. the street, sidewalk, wall,etc.) that has a 50 percent maximum foot-candle measurement at an anglegreater than 15 degrees from the centerline of the illumination pattern.This is referred to in the lighting field as the half-maximum point. Alight source with a 15 degree half maximum measurement is also describedas a 30 degree FWHM (Full Width, Half Maximum) light source.

Since light energy dissipates as the square of the distance from thesource and there is additionally a cosine falloff based on the angle ofincidence with respect to the illuminated plane, a wide angle beam oflight requires considerably more intensity at high angles from itscenterline than at its centerline. A good metric to use to analyze therequired intensity is an iso-candela map. This radial map showsintensity verses degrees from the centerline of a light source or aluminaire.

The preferred embodiment of the invention has a transparent ‘blob-like’or complexly shaped lens, most likely of plastic or glass, thatoptically modifies light from the LED to generate the high angleintensity required for the wide beam angles without adding much if anyadditional reflective or refractive surface losses, other than what theLED packaging causes itself. The complex shape of the lens is determinedby a transfer function that is disclosed below. It is the lack ofadditional surface losses that allow the preferred embodiment of theinvention to be extremely efficient. However, it must be expresslyunderstood that the scope of the invention contemplates designs that maydepart from this efficiency standard to accommodate manufacturingartifacts or other compromises for the sake of economic production. Inthe preferred embodiment of the invention the lens is ‘glued’ to theoriginal LED protective cover with an index matching material so as tovirtually eliminate the seam between the two. In another preferredembodiment of the invention the lens is integrally manufactured into theprotective dome or cover of the LED package.

The ‘blob’ zone is a small concentrating lens zone that is formed alongthe desired primary director of the device. This blob zone of the lenscollects the light rays emitted by the LED and sends them along apredetermined direction, i.e. the primary director, dependent on thebeam angle desired by the optical designer. In the illustratedembodiment, the lens will be first considered to be a surface ofrevolution with a centerline or axis aligned with the centerline of theLED light pattern. However, additional embodiments will be disclosedwhere this azimuthal symmetry is broken. The nearby surrounding surfaceof the lens to the blob zone also collects light from the LED emitterand refracts it toward the preferential direction. The shape of thecentral forward cross-section of the lens gently apportions the energyin the segment from the directed blob zone to the centerline. Theinterior cross-sectional surface of the lens that is struck by theperipheral energy of the LED emitter is in a preferred embodimentundercut to either refract the light rays toward the preferentialdirection and/or internally reflect the light rays through the forwardsurface of the lens. The undercut surface of the lens is characterizedby a smaller outer diameter defined from the centerline of the lens atthe base of the lens than the outer diameter of the lens in the blobzone. In other words, the surface of the lens falls away or narrows atsome point as the base of the lens is approached. Typically, an undercutsurface could not be made in a single-piece mold, but would require amultiple piece mold for release. In the preferred embodiment of theinvention, almost all the energy of the LED is directed into theradiated beam without losses in excess of those generated by the LEDwithout the invention deployed. Again, this is not to be understood as alimitation of the invention, which may include embodiments where greaterlosses than the native LED losses are permitted for various economic ormanufacturing conveniences.

One of the preferred embodiments of the invention generates a beam thathas a differential of angles, and therefore intensities, in its twoprimary axes. In this instance the ‘blob’ cross-section of the lensvaries as a function of the azimuthal angle about the centerline axis.This embodiment is intended for use in street lights and walkway lightsor any use where there is a requirement for an asymmetrical oranamorphic beam. The iso-candela map of such a luminaire is nonuniformabout its axes. Although it would be unusual, it is neverthelesscontemplated within the scope of the invention that there could be morethan two lobes along the opposing axes, such as a three, four or evenmore ‘blob’ axes.

One LED is hardly ever enough for a street light or parking lot light,so it is the preferred embodiment of the invention that a plurality ofdevices would be utilized in an array. It is expected that such an arraymight also be devised with two or more different ‘blob’ opticalconfigurations to enhance the overall beam pattern. In the preferredembodiment, the array is disposed in a flat or planar arrangement as amodule that can be readily scaled in size.

The device is generally described as being used in the field of generallighting illumination, but it could be used in niche markets in thefield of lighting and illumination as well. Uses of the inventioninclude, but are not limited to, street lighting, parking structurelighting, pathway lighting or any indoor or outdoor venues where a broadbeam of light is desired, and is either azimuthally symmetric or biasedin one or more axial directions. The illustrated embodiment can also beused to advantage in mobile lighting in vehicles, aircraft, trains,vessels and the like. The number and variety of applications in whichuse can be made are too numerous to even attempt to list.

While the drawings may describe what appears to be a simple concept, theshort distance from a relatively large emitter to small surface presentsmany design challenges. Even a very small, 0.002″, change in surfaceposition or curvature or small angle change, 0.05 degree, can throw theintended beam into disarray with bad visual artifacts or ‘rings’ in theresultant beam.

In another embodiment of the invention, a beam is generated that isoffset in one or more axes from the projected centerline of the device.The resultant beam can be used, for example, to generate a Type IIIroadway lighting luminaire which requires a beam pattern that has itsprimary director to be offset from its nadir. The lens appears to be afreeform shape with cross-sections that that may have tilted lobes andsurfaces that cause individual rays of the beam to refract in a skewedmanner. In addition to the surfaces that define the majority portion ofthe beam, the embodiment also includes additional surface shapes, like acomplex prism, that add further control to the composition of thecomposite beam. It is also anticipated that facets, Fresnel typeflattening of surface shapes in the form of complex prism, diffusingtechniques or other surface enhancements may be added to lens to obtaina certain effect within the beam.

The term, beam, is not often associated with highly divergentillumination devices, but it is used in this specification to describethe collectively formed output of the device, and is not necessarilylimited a narrow beam of light.

Turn now to FIGS. 1-4 wherein the details of the illustrated embodimentof the invention depicted is azimuthally symmetric. FIG. 1 is anorthogonal top plan view of the device, generally denoted by referencenumeral 10. FIG. 2 shows the device 10 in a cross-sectional view inposition on LED 1, which is a conventional packaged LED. LED emitter 2is positioned on the axis of the device 10 and in the embodiment shownthe emitter 2 is centered in a hemispherical cavity (not shown) definedin a transparent, hemispherical protective dome 19 of the device 10. Inthis embodiment the hemispherical cavity is filled with a material whoseindex of refraction matches that of the protective dome 19 of the LED 1to virtually eliminate the cavity defining interior surface of dome 19from causing any losses or providing any refraction. In FIG. 2 threesolid angles or zones of interest, A, B and C, are depicted. These zonesare for reference only and some embodiments of the invention may havemore or fewer zones. As shown, zone A represents surface 5 of the lens21 into which the forward solid angle of energy emitted from LED emitter2 is collected, represented by rays 11 and 12. Ray 11 is transmittedwithin the lens 21 from emitter 2 to the surface of lens 21 and ray 12is the refracted into zone A through the surface of the lens 21. Zone Brepresents the surface 4 of the lens 21 referred to as the ‘blob’ zone.This surface 4 is situated on either side of the intended main director6 at the approximate angle of the beam's highest desired intensity. ZoneC represents the undercut surface 3 which collects the remainingperipheral forward solid angle of energy from the LED emitter 2 asrepresented by rays 7, 8 and 9. Ray 7 is transmitted from emitter 2 tothe surface 3 within lens 21, is totally internally reflected as ray 8and then is refracted by surface 5 as ray 9. However, it must beunderstood that some or, if desired, most of the rays from emitter 2incident on surface 3 will not be internally reflected, butintentionally refracted through surface 3 as peripheral rays.

Optional flange 13 can be of most any desirable shape and is utilizedfor sealing the device 10 and/or any proximate portion of a light modulemanufactured with the device as described below. The shape of flange 13may be configured to provide for indexing or azimuthal alignment to afixture in which device 10 of FIGS. 1-4 or particularly device 20 ofFIGS. 5-9, whose radiation pattern is not azimuthally symmetric, is setor may provide a snap fit connection of device 10 into the fixture.

In FIG. 2, surface 3 of the depicted embodiment of the invention 10 canbe designed to be either totally internally reflective (TIR) orrefractive or both. Surfaces 4 and 5 are intended to be primarilyrefractive.

The method used to design the embodiment shown is to first select theprimary director angle .delta. for the highest intensity, shown in thepolar graph of FIG. 3 as point 14. It has been determined by empiricaltesting that if this director angle passes much beyond 60-62 degreesfrom the centerline, the resultant effect is to limit the ability of thedevice 10 to perform its primary task of providing a significantincrease in the iso-candela plot of the off-axis energy as shown bypoint 14 of FIG. 3 and still achieve the goal of a smooth, useful beam.In the embodiment of FIG. 3 the maximum intensity occurs at about 52degrees off axis.

In cross-section, surface 4 of zone B is defined as an arc which has itscenter disposed along the director 6. The radius and the start and endangles of the arc defining surface 4 are variables defined by iterationwith the surface definitions of zones A and C. The surface 5 is definedas a concave refractive surface intended in this embodiment to ‘spread’the central solid angle of energy from the LED emitter 2 outward fromthe centerline. The merge point of surfaces 4 and 5 between zones A andB is found by construction. In the embodiment shown, surfaces 4 and 5are tangent to each other or smooth at the merge point. However, it isnot a requirement of the invention that they be tangent. Surface 3 ofzone C is also defined in the embodiment shown as a surface generated bya tangent arc. It could, however, be generated by a line of revolutionof any shape or slope. By using the tangent arc for surface 3 of zone C,some of the emitted rays incident on surface 3 from emitter 2 refractoutward and some are totally internally reflected and proceed throughthe forward surfaces 4 and 5 of zones A and B. By controlling the arcradius and the segment angle of surface 3, the resultant beam can bedefined in total and will include almost all the energy emitted by LEDemitter 2. Measurements have shown that the resultant beam can includevirtually the same number of lumens into an integrating sphere as theoriginal LED does without lens 21.

Manipulation of the shapes of surfaces 3, 4 and 5 of FIG. 2 can beperformed until the desired intensity ratios and angles of intensity arerepresented in a polar candela distribution plot of the design asdepicted in FIG. 3. It must be understood that surfaces 3, 4 and 5 couldbe represented by any number of differently shaped surfaces includingone or more which are point wise defined, rather than geometric shapesin zones as depicted. It is within the scope of the invention that theshape of the profiles of surfaces 3, 4 and 5 could be derived bycomputer calculation as a function of the desired beam profile asdefined in the polar candela distribution plot and the resultantsurface(s) profile used as the surfaces of revolution in the case of aradially symmetric design.

FIG. 4 shows the result of a ray trace of the device 10 of FIGS. 1 and2. The rays have been reduced to a small percentage of those traced tobetter show the effects of rays as they react to the surfaces 3, 4 and 5of each of the above described zones A, B and C. Of course, it isunderstood that light rays from a ray trace only simulate the effects oflight energy from a light source.

FIG. 5 shows a three quarter perspective view of another preferredembodiment 20 of the invention whereby the resultant beam energypattern' is not azimuthally symmetric. Circular lip 18 of FIGS. 6-9represents a sealing feature that optionally allows the device 20 to besealed when built into a light fixture or an array. The cross sectionalview of FIG. 9 is taken through section line D-D of FIG. 5. The top planview of the device 20 is represented by the diametrically opposing‘blob’ segments 14 and the diametrically opposing smoother side segments15 azimuthally orthogonal to the blob segments 14. It is easier tounderstand these profiles by looking at FIGS. 7 and 8, which show theprofiles of the segments 14 and 15 from both horizontal and verticaldirections respectively, and FIG. 6 which shows the device 20 in arotated oblique view that shows its elongated profile. It can be seen inFIG. 7 that the illustrated profile in this view is similar to thedevice 20 shown in FIGS. 1 and 2. However, the similarity is lost whenyou examine the azimuthally orthogonal profile of FIG. 8. The ‘blob’shape in the embodiment of FIG. 7 is defined by multiple cross-sectionsof segments 14 and 15 rotated about the centerline 23 in which thesurface of lens 21 is lofted between cross sections of segments 14 and15 much like the lofting of a boat hull. By manipulating the shape ofcross-sections of segments 14 and 15, the ‘blob’ or lobed segment 14 isdefined as well as the smoothing of surface segments between thediametrically opposing ‘blobs’ or lobes 14. Lofting is a draftingtechnique (sometimes using mathematical tables) whereby curved lines aredrawn on a plan between cross sectional planes. The technique can be assimple as bending a flexible object such as a long cane so that itpasses over three non-linear points and scribing the resultant curvedline. or plotting the line using computers or mathematical tables.Lofting has been traditionally used in boat building for centuries. whenit is used to draw and cut pieces for hulls and keels. which are usuallycurved. often in three dimensions.

In the view of FIG. 9 it can be seen that the ‘blob’ or lobe segment 14is defined similarly to the device 10 shown in FIG. 2. The zones A, Band C of the embodiment of FIG. 9 are similar as are the rays 25, 26 andrays 32-34 are similar to analogous rays 12, 11, 7, 8 and 9 respectivelyof FIG. 2. The undercut surface 31 as shown is flat, but it could be anyshape or angle that provides the desired result. The undercut surface 31of FIGS. 5-9 or surface 3 of FIGS. 1-4 differs from undercut surfaceswhich can be found in conventional total internal reflectors (TIR) inthat the surfaces of the conventional TIR are located in what would betermed the far field of the LED and not its near field. In the presentinventions surfaces 3 and 31 are near field surfaces in that they areoptically closely coupled to the LED source and ideally have no air gapor at least no substantial air gap between the LED and the surface 3 or31. Further, in a conventional TIR the undercut surfaces are generallyused as reflective surfaces and to the extent that there are refractedrays emitted through such surfaces, the rays are lost to the useful beamor what is the intended beam of light. In the present invention theundercut surfaces 3 and 31 optically contribute to the intend beam to amaterial degree, both in the reflected as well as the refracted raysincident on them.

LED emitter 29 is disposed approximately at the center of thehemispherically shaped surface 17 of FIGS. 7 and 8, which matches theshape of dome 19. LED package 28 and the device 20 are optionally bondedwith an index matching material at surface 17 of lens 21 and the dome 19of the LED package 28. It is contemplated by the invention that thedevice 20 be incorporated in the production of the LED package 28 in analternate embodiment whereby the manufacturer of the LED does not bond aseparate lens 21 to the LED; however, the lens 21 of device 20 is theprotective dome of the LED package 28 itself. In either case, theresultant devices 20 shall be very similar optically. The mechanicalfeatures at the base of the device are optional and may be utilized ornot.

FIG. 10 shows a two dimensional iso-foot-candle plot of the output ofthe device 20 shown in FIGS. 5-9. It shows the anamorphic shape of theoutput beam which is nearly two times the length/width ratio of aazimuthally symmetric beam of the embodiment of FIGS. 1-4. FIG. 11 showsthe polar iso-candela plot with overlaid angles of candela data. Theplot 35 is the intensity distribution as seen in the horizontal plane ofFIG. 7, plot 38 is the intensity distribution as seen in the azimuthallyorthogonal plane of FIG. 8, and plot 36 is the intensity distribution asseen in a plane at 45 degrees or half way between the views of FIG. 7and FIG. 8. The maximum of intensity distribution pattern decreases asthe view rotates from the plane of FIG. 7 to the plane of FIG. 8 asshown in the plots 35, 36 and 38 and the decreases in angle or rotatesupwardly from about 52 degrees to about 40 degrees off axis.

FIGS. 12 and 13 are ray trace plots of the device of FIGS. 5-9. Theseplots show graphically the path of energy from the LED emitter 29 in theplanes corresponding to FIGS. 7 and 8 respectively. As in the device 10of FIGS. 1 and 2, the surface of zone C of FIG. 9 is both refractive andtotally internally reflective in this embodiment of the invention.

FIGS. 14 and 15 illustrate a further embodiment of the invention whichincorporates a plurality of devices 21 or 20 of the invention by which alight module 40 is provided. This light module 40, either individuallyor in multiple copies, can be the basis of a flat luminaire that is usedfor street lighting, pathway lighting, parking structure lighting,decorative lighting and any other type of spread beam application. Lightmodule 40 is shown as a rectangular flat bar, but can assume any twodimensional planar shape, such as square, circular, hexagonal,triangular or an arbitrary free form shape. Inasmuch as light module 40is flat it can be mounted in its corresponding fixture parallel to thetwo dimensional plane that it is intended to illuminate, such as thestreet, walk or floor. This results in the light be directed in a spreadbeam toward the useful two dimensional pattern for which it is intendedand not skyward or in other nonuseful directions. The light module 40 isa very simple and low cost means to provide LED lighting to luminairemanufacturers where the light module 40 can be treated in the designs ofas a single ‘light bulb’. With the addition of heat sinking and powerincorporated on or into module 40, the light module 40 can be easilyincorporated into existing luminaires or integrated into new designs.

The exploded view of the light module 40 in FIG. 14 shows a disassembledconventional LED package 28 and the ‘blob’ lens 21 which is disposedonto LED package 28. FIGS. 14 and 15 further show a flat heatdissipating carrier 41 to which the LEDs 28 are attached. The flatcarrier 41, which is typically made of metal, such as a heat conductivealuminum alloy, could provide just enough heat dissipation andconduction to allow proper cooling of the LED with the addition of aproperly designed heat sink or other heat dissipating means, or thecarrier 41 could be the entire heat sink or other heat dissipating meansitself. A printed circuit board 46 is shown as a convenient means toprovide power to the LEDs 28, however it could be eliminated and theLEDs could be wired to each other directly. Additional means ofconveying power to the LEDs 28 are contemplated by the invention. Thewires 42 shown are just one means of providing power to the light module40. Connectors, sockets, plugs, direct wiring and other means areequivalent substitutes. The light module is covered by a moldedcomponent 43 or a co-molded cover 43 or any other means of providing aseal, such as a potting compound, or optionally no seal at all. Anoptional potting compound, which is forced or disposed between cover 43and carrier 41, is just one means of providing sealing for the lightmodule 40, rendering it in such an embodiment as waterproof orsubmersible. The assembled module 40 as shown in FIG. 15 can includehold down features, alignment features as well as other conventionalfeatures desired for implementation into a luminaire.

FIGS. 16-20 depict another preferred embodiment of the invention whereinthe resultant ‘beam’ of light energy is directed in a skewed fashionwith respect to the centerline of the device 20. The beam can be definedas having ‘lobes’ of intensity that are not coincident with the primaryaxes of the device 20. The device shown in FIG. 16 is similar to FIG. 6in all respects with two exceptions, first there a complexly shapedprism 50 is provided on the top of lens 21 and the second is describedas follows. As best shown in the top plan of FIG. 17 lobes 14 aresimilar to lobes 14 in FIG. 5 while the flattened sides 15 are slightlyradially extended with a central bulge. Prism 50 is complexly shaped toprovide a means for directing light in zone A into a direction which ismore dramatically skewed relative to centerline 23. In addition, as bestshown in FIG. 20 the top surface 5 is angled off axis to further skewthe light in the same general direction to which prism 50 is directed.Prism 50 has at least four separately definable surfaces, which in planview vaguely resemble the top plan surface of a toilet and water closet.The surfaces are empirically determined by trial and error from thedesired skewed polar candela plot and are strongly dependent thereon.Therefore, the surfaces of prism 50 will not be described in greaterdetail other than to specify that the net effect is to redirect thelight incident on prism 50 from within lens 21 toward one side of thelight pattern skewed relative to the centerline 23.

Turn now to FIGS. 21-26 wherein another embodiment of the invention isdepicted. FIG. 21 is a perspective view of the device, generally denotedby reference numeral 10. FIG. 22 shows the device 10 in anotherperspective view. Optional flange 30 is shown to have a keyed shape thatallow the lens 21 to be rotationally indexed in an assembly or fixture(not shown). The flange 30 may also be utilized to seal the LED housedin lens 21 into an assembly by a mating part (not shown) that interfacesor interlocks with the flange 30. Optional seal 18 is shown as a part ofthe flange 30 and may be incorporated into it by many different means.

Surfaces 57 and 58 of lens 21 are utilized to direct the energy from theLED's peripheral beam, which is defined as the energy radiating in thesolid angular zone from a horizontal plane parallel to the plane of theLED emitter to approximately 45 degrees from the perpendicularcenterline of the LED emitter, while surfaces 51, 52 and 59 direct theenergy in the solid angular zone from the LED's centerline toapproximately 45 degrees from the centerline, the primary LED director.One very important element of the invention is the zone of the lens 21depicted by surfaces 51 and 70. The surfaces 51 and 70 form theprinciple parts of a complex prism on the surface of lens 21, which iscalled a “Pope's hat”. The solid angle zone of the light served bysurfaces 51 and 70 takes the energy from the primary directed beam ofthe LED's ‘curb’ side and redirects it toward the ‘street’ side.

Optional surface 53 is a blended contour between surfaces 52 and 58.Surface 57 is mirrored across intersection 54 in FIG. 23 and is loftedin the embodiment shown to redirect the centerline energy of the LEDdown the ‘curb’ direction and across the centerline. Surface 57 allowsfor very high efficiency for the lens 21 in both the street and the curbside of its light pattern.

In FIG. 23, surface 52 is depicted as an azimuthally symmetric surfaceddefined through an azimuthal angle of about 185 degrees. While this isdesirable for some applications it is well within the scope of theinvention that surface 52 and its adjacent surfaces may be azimuthallyasymmetric. Surface 59 is an optional feature to redirect the centerlineenergy of the LED. Surface 59 can take of many different forms to allowthe designer freedom to shape the beam. In the embodiment of FIGS. 21-26the shape of surface 59 is utilized to allow for a continuation of thelight spreading effect of surface 52, but constrained to keep thethickness of the device 10 within manufacturing capabilities.

In FIG. 24, interface 62 between dome 19 and lens 21 is utilized if thelens 21 is a molded optic separate from the LED. If the lens 21 of thedevice 10 were molded directly on or assembled by the manufacturer onthe LED emitter, interface 62 does not exist. Interface 62 is comprisedof the two mating surfaces of the LED dome 19 and the inside of the lens21. It would be most desirable if the interface were bonded with anindex matching cement or a thixtropic index matching material wereretained in interface 62. Using an index matching material, opticalmeasurements have shown that the resultant beam from the assembleddevice 10 can include virtually the same number of lumens into anintegrating sphere as the original LED does without lens 21.

The nadir 74 of the device 10 is shown in FIG. 27 as well as is thehorizon 72 and the ‘street’ side angle marker 73. The rays 70 of maximumcandela of the resultant beam are illustrated in the rightmost portionof the drawing. FIG. 28 is a rotated three dimensional view of the samecandela map as FIG. 27 and shows the plot as it would be seen from thecurb side of the pattern at the bottom portion of the view. The abilityof the various surfaces of lens 21 described in FIGS. 21-26 to throw ortransfer energy from one side of the Lambertian output of theconventional LED to one side of the illumination pattern is graphicallyillustrated. Note also that all the rays are directed in FIG. 27 in adownward direction with little if any energy in the direction of horizon72 or upward. Sky rays are virtually eliminated.

Manipulation or modification of the shape and position of surfaces 52,53, 58, 57, 54, 51, 70 and others defining lens 21 as shown in FIGS.21-23 can be performed until the desired intensity ratios and angles ofcandela are represented in a ray trace of the design as depicted inFIGS. 27 and 28 or modifications thereof according to the teachings ofthe invention. It must be understood that the lens surfaces could berepresented by any number of separate surfaces including one or morewhich are defined by a point wise transfer function rather thangeometric segmental shapes. It is entirely within the scope of theinvention that the shape of the profiles of the lens surfaces could bederived by a computer calculation derived from a predetermined beamprofile and the resultant lens surface(s) profile(s) then used as thecross-section(s) of various portions of the lens 21 according to theteachings of the invention.

FIG. 29 is a plot of the two dimensional distribution of energy as itstrikes the surface of the ‘street’ below the device 10. This plotgenerally would be described with iso-intensity contour lines in unitsof energy such as foot-candle or lux. The device 10 is centered in thedrawing of FIG. 29 with the ‘street’ side to the right of center and the‘curb’ side to the left of center. The plot is symmetry about ahorizontal line running from the curb to the street with identicalintensity patterns in the top and bottom portions of the drawing.

FIG. 30 is a ray tracing of the device 10 of FIGS. 21-26 as seen in aside view reversed from that shown in FIG. 25. The rays have beenreduced to a small percentage of those which could be traced to bettershow the effects of rays as they are redirected from the Lambertianpattern of the LED housed within lens 21 by the surfaces of the lens 21.Rays 82 correspond to the rays directed by surface 52. Rays 83 aredirected by undercut surface 58. FIGS. 24-26 show a small undercutportion of surface 58 which extends partially around the base of lens21. Surface 57 in the view of FIG. 25 has no or little undercut, whilethe basal portions of surface 58 have a small undercut which smoothlytransitions into surface 57. It should be noted in FIG. 30 that rays 80which are redirected from surface 51 show that surface 51 is acting as aTIR reflector of the beam energy from the LED on the ‘curb’ side totransfer energy to the ‘street’ side. Rays 81 are refracted LED energyin a direction away from the centerline of the LED beam pattern. Strayrays 81 show losses which arise in the lens 21 as a result ofmanipulating the beam pattern.

The emitter 29 in the LED is assumed above to be a Lambertian emitter.The concept of using a ‘floating’ reflective surface on the ‘curb’ sideof lens 21 to reflect light to the ‘street’ side of a lens 21 isexpressly included within the scope of the invention even when using HIDor other light sources with different emission patterns. Any kind oflight source now known or later devised may be employed in the disclosedcombination of the invention with appropriate modifications madeaccording to the teachings of the invention. Wherever in thisdescription the terms associated with streetlights are used, such as‘street’ side or ‘curb’ side, they could be substituted with other termsthat describe offset beam patterns in general.

FIG. 31 is another cross-section view of a ray tracing of the embodimentof FIGS. 21-26 as seen in a frontal view of FIG. 26. The rays radiatingfrom the side plan view of FIG. 26 are refracted toward the streetsurface. Rays 91 represents the energy from the LED in the primary zonerefracted outward by the surface 52 of FIGS. 21-26. Again few if anyrays directed toward the horizon are present.

FIG. 32 is a solid cross-sectional view of device 10 as seen throughline F-F of FIG. 23. FIG. 32 shows an LED with emitter 29 with lens 21optionally glued in place with the interface 62 or seam bonded with anindex matching cement. The optional flange 30 can be seen as a sealingfeature to mate with additional components of an assembly (not shown).Surface 57 represents the transition between the ‘street’ side profilesand the ‘curb’ side profiles of lens 21 that mainly refract light towardthe street from the peripheral Lambertian beam of the LED. Moreparticularly, surface 57 is divided into two subsurfaces by a centerline54 in the embodiment of FIGS. 21, 23 and 24, which subsurfaces spreadthe light in the beam outward from the centerline 54 in larger angles.For example, if in one embodiment centerline 54 were perpendicularlyoriented to the curb in a street light installation, the subsurfaceswould spread the beam transmitted through surface 57 in directions moreparallel to the curb and away from the centerline 54. Surface 51primarily reflects energy from the LED primary light direction from the‘curb’ side toward the ‘street’ side.

FIG. 33 summarizes an overall conceptualization of the methodology ofthe invention. The problem solved by the invention is defined by twoboundary .conditions. namely the light pattern of the light source whichis chosen at step 100 and the two dimensional iso-foot candle plot whichis to be projected onto the surface which is intended to be illuminatedin step 106. In the illustrated embodiment the problem of providing awide beam street light pattern is assumed for the boundary condition ofstep 106 and the Lambertian pattern of an LED is assumed in the boundarycondition 100. Thus. it can readily be understood that the same problemdefined by different characterizations of the boundary conditions ofsteps 100 and 106 are expressly included within the scope of the claimedinvention. For example, if has already be expressly mentioned thatboundary condition 100 need not assume the Lambertian pattern of an LED,but may take as the boundary condition the three dimensional energydistribution pattern of a high intensity discharge (HID) lamp. Lightsources which do not assume the Lambertian pattern of an LED. like ahigh intensity discharge lamp are defined for the purposes of thisspecification as non-Lambertian light sources.

The problem then becomes recast as how to get the shape of a lens oroptic 21 which provides the needed transfer function between the twoboundary conditions of steps 100 and 106, namely the three dimensionalenergy distribution pattern of the light source to the projected twodimensional illumination pattern for the target surface. The problem isnontrivial.

The solution for an asymmetric broad or spread beam has been disclosedin connection with FIGS. 1-32 above and the related specification. Oncea three dimensional lens shape is determined at step 102 as shown inFIGS. 1-9, 16-20 and 21-26, the three dimensional candela plot as shownin FIGS. 11, 27 and 28 and as suggested by the ray tracings of FIGS. 12,13, 30 and 31 can be mathematically derived using conventional opticalcomputer aided design programs, such Photopia® sold by LightingTechnologies of Denver, Colo., assuming the three dimensional energydistribution of the light source, e.g. a Lambertian distribution in thecase of an LED.

Given the three dimensional candela plots, the two dimensional iso-footcandle plots of FIGS. 10 and 29 can be mathematically derived usingconventional optical computer aided design programs. The resultsobtained are then compared to the boundary condition of step 106. To theextent that the boundary condition of step 106 is not satisfied, theoptical designer through trial and error can modify the threedimensional shape of lens 21 in step 102 and again repeat steps 104 and106 in a reiterative process until the desired conformity with thetarget two dimensional iso-foot candle plot is obtained.

The invention also includes the methodology where the needed lens shapeis rendered mathematically through an analytical process or numericallythrough a numerical reiterative estimation process with the boundaryconditions of steps 100 and 106 as numerical inputs consistent with theteachings of the invention.

It can also thus be appreciated that a plurality of such devices canthen be combined into an array of devices. Each device in the array hasthe same three dimensional energy distribution pattern that results inthe same intended two dimensional illumination pattern on the targetsurface or street. When a plurality of such devices are closely spacedtogether in the array relative to the size of the illumination patternon the target surface or street, their respective illumination patternsare substantially linearly superimposed on each other to provide thesame illumination pattern on the target surface or street as produced bya single device, but with the increased intensity of the plurality ofdevices in the array. Similarly, the arrays can be manufactured in amodular fashion, so that a plurality of arrays combined together canstill have a relatively small size compared to the distance to or thesize of the illumination pattern on the target surface or street, thatthe illumination pattern of each array substantially overlays the sameillumination pattern of all the other arrays in the collection. Hence,the intensity of the illumination pattern on the target surface from thecollection of arrays can be scaled without substantial modification ofthe illumination pattern by modular scaling of the arrays into larger orsmaller collections.

Many alterations and modifications may be made by those having ordinaryskill in the art without departing from the spirit and scope of theinvention. Therefore, it must be understood that the illustratedembodiment has been set forth only for the purposes of example and thatit should not be taken as limiting the invention as defined by thefollowing claims. For example, notwithstanding the fact that theelements of a claim are set forth below in a certain combination, itmust be expressly understood that the invention includes othercombinations of fewer, more or different elements, which are disclosedin above even when not initially claimed in such combinations.

The words used in this specification to describe the invention and itsvarious embodiments are to be understood not only in the sense of theircommonly defined meanings, but to include by special definition in thisspecification structure, material or acts beyond the scope of thecommonly defined meanings. Thus if an element can be understood in thecontext of this specification as including more than one meaning, thenits use in a claim must be understood as being generic to all possiblemeanings supported by the specification and by the word itself.

The definitions of the words or elements of the following claims are,therefore, defined in this specification to include not only thecombination of elements which are literally set forth, but allequivalent structure, material or acts for performing substantially thesame function in substantially the same way to obtain substantially thesame result. In this sense it is therefore contemplated that anequivalent substitution of two or more elements may be made for any oneof the elements in the claims below or that a single element may besubstituted for two or more elements in a claim. Although elements maybe described above as acting in certain combinations and even initiallyclaimed as such, it is to be expressly understood that one or moreelements from a claimed combination can in some cases be excised fromthe combination and that the claimed combination may be directed to asubcombination or variation of a subcombination.

Insubstantial changes from the claimed subject matter as viewed by aperson with ordinary skill in the art, now known or later devised, areexpressly contemplated as being equivalently within the scope of theclaims. Therefore, obvious substitutions now or later known to one withordinary skill in the art are defined to be within the scope of thedefined elements.

The claims are thus to be understood to include what is specificallyillustrated and described above, what is conceptionally equivalent, whatcan be obviously substituted and also what essentially incorporates theessential idea of the invention.

We claim:
 1. A street luminaire comprising: a fixture operable toposition a plurality of light modules overhead relative to a street tobe illuminated; and the plurality of light modules, each light modulecomprising: a planar substrate; and a number of light sources arrangedin a two-dimensional array and mounted to the planar substrate, eachlight source comprising: at least one light emitting diode; and a lensmounted to accept light from the at least one light emitting diode,wherein the lens exhibits symmetry with respect to a first referenceplane that extends through the lens and the planar substrate, wherein asecond reference plane extends through the planar substrate and the lensand is perpendicular to the first reference plane, wherein the lenscomprises a feature that is disposed on a first side of the secondreference plane, and wherein the feature is operative to receive lightpropagating on the first side of the second reference plane and toredirect said received light through the second reference plane forpropagation on a second side of the second reference plane so that theeach light source outputs a respective pattern of light that is biasedstreet side relative to curbside and that has a respective intensity,wherein each light module is operative to produce a pattern of lightsubstantially matching said respective pattern of light with anintensity that is substantially equal to said respective intensitymultiplied by the number.
 2. The street luminaire of claim 1, whereinthe feature comprises a prism.
 3. The street luminaire of claim 1,wherein the feature comprises a refractive surface.
 4. The streetluminaire of claim 1, wherein the lens comprises a depression disposedat an intersection between the first reference plane and a surface ofthe lens, the depression biased to one side of the second referenceplane.
 5. The street luminaire of claim 1, wherein the fixture positionsthe plurality of light modules such that the first reference plane issubstantially perpendicular to the street and the second reference planeis substantially parallel to the street.
 6. The street luminaire ofclaim 1, wherein each light module comprises: at least one heat sink;and circuitry that is operable to supply electrical power to the lightemitting diodes.
 7. The street luminaire of claim 1, wherein each lightmodule comprises a heat sink that conducts and dissipates heat.
 8. Astreet luminaire comprising: a plurality of light modules; and a fixturethat is operable to position the plurality of light modules forilluminating a street that extends in a direction, wherein each lightmodule comprises: a substrate; and a number of light sources disposedalong the substrate to form an array of light sources having asubstantially planar format, each light source comprising: a respectivelens; and at least one respective light emitting diode coupled to therespective lens, wherein the respective lens is intersected by a planethat extends in the direction, the plane having a street side and acurbside, and wherein a jutting portion of the respective lens isdisposed on a curbside of the plane and is operative to receive lightfrom the at least one respective light emitting diode that is headedcurbside and to reflect said received light to pass through the plane,so that the respective lens produces an illumination pattern of anintensity, the illumination pattern biased street side relative tocurbside, and wherein each light module produces the illuminationpattern of a second intensity that is approximately equal to theintensity multiplied by the number.
 9. The street luminaire of claim 8,wherein the respective lens has a plane of symmetry that issubstantially perpendicular to the plane.
 10. The street luminaire ofclaim 8, wherein the jutting portion of the respective lens comprises atotally internally reflective surface.
 11. The street luminaire of claim8, wherein the plurality of light sources disposed along the substrateform a two-dimensional array, and wherein all of the planes aresubstantially parallel to one another.
 12. The street luminaire of claim8, wherein the fixture is further operable to position the plurality oflight modules substantially parallel to a surface of the street.
 13. Thestreet luminaire of claim 8, wherein when cast on a street surface, theillumination pattern is substantially symmetrical with respect to a lineon the street surface that runs perpendicular to the plane.
 14. Thestreet luminaire of claim 8, wherein the illumination pattern forms atwo-dimensional distribution of energy on a surface, and wherein thetwo-dimensional distribution of energy is divisible into two intensitypatterns exhibiting mirror image symmetry with respect to one another.15. A street luminaire comprising: a first number of light modules, eachoperable to produce an illumination pattern of a first intensity; and afixture that is operable to mount and power the first number of lightmodules to produce the illumination pattern of a second intensity forilluminating a street, the second intensity substantially equaling thefirst intensity multiplied by the first number, wherein each lightmodule comprises: a substantially flat substrate; and a second number oflight sources arranged upon the substantially flat substrate, each lightsource comprising: at least one respective LED; and a respective lenscomprising a first side that the fixture orients curbside and a secondside that the fixture orients street side, wherein the first side of therespective lens and the second of the respective lens are opticallydifferent from one another, wherein the respective lens is mounted withthe at least one respective LED such that the first side of therespective lens receives light from the at least one respective LED andthe second side of the respective lens receives light from the at leastone respective LED, wherein the first side of the respective lens isoperable to send street side a substantial amount of the light that thefirst side of the respective lens receives, resulting in biasing theillumination pattern street side relative to curbside, and wherein therespective lens is operable to produce the illumination pattern of athird intensity, and the first intensity substantially equals the thirdintensity multiplied by the second number.
 16. The street luminaire ofclaim 15, wherein the respective lens exhibits optical symmetry withrespect to a centerline that is substantially perpendicular to thestreet.
 17. The street luminaire of claim 15, wherein the at least onerespective LED provides an axis that is perpendicular to thesubstantially flat substrate, and wherein the respective lens comprisesan outer surface comprising a depression biased on one side of the axis.18. The street luminaire of claim 15, wherein the respective lenscomprises a complex prism jutting from the first side of the respectivelens.
 19. The street luminaire of claim 15, wherein the illuminationpattern provides a two-dimensional distribution of energy on a streetsurface, the two-dimensional distribution of energy divisible into twointensity patterns exhibiting mirror image symmetry with respect to oneanother.
 20. The street luminaire of claim 15, wherein the second sideof the respective lens and the first side of the respective lens differfrom one another due at least to one different internally reflectivefeature and one different refractive feature.